The denarius was a small silvercoin used by the Roman Empire and Roman Republic. The denarius weighed about 3 to 4.5 grams. It was the main coin of Ancient Rome. It became the most common coin produced for circulation but was slowly debased in weight and silver content. The coin was then sometimes made of copper and painted silver in color. During the Empire the front side usually had a picture of the emperor on it.

The denarius was introduced in 211 BC, and was last issued in 275 AD, by which time it was made of bronze.